Born in Neu-Ulm, and a blacksmith by trade, he joined Carl Wilhelm Schmidt and Christopher Eipper at the Zion Hill Mission in what is now the Brisbane suburb of Nundah in Queensland.
After the mission closed, Zillmann stayed in the area and turned to farming.
"On 31 May 1858, John Leopold Zillman purchased Portion 162, consisting of 29 acres 3 roods in area on Sandgate Road.
In 1864 the land was bought by Thomas Ward, William Clayton and George Paddle.
He discussed the perceived successes and failures of the Mission in regard to Aboriginal people, and gave his opinion on the causes of frontier conflict.